Legal advice on a dispute with Engie

Left Belgium years ago. A debt collector has chased me down to claim an unpaid debt of about Eur50 and is now claiming over Eur1000. Its all in Dutch so I cant understand it and I can find no explanation or breakdown of this claim in the correspondence. Can anyone advise on a legal person/lawyer to whom I can speak about this matter? Im trying for months to dispute it but getting a brick wall. Thanks